Mexican security forces say they have caught the leader of the cocaine-trafficking Gulf Cartel, the second major gang boss to be captured in just over a month.

Mario Ramirez Trevino, known as X-20 or The Bald One, was captured in Mexico's northern Tamaulipas state by the Mexican military, media reported.

Ramirez had not long been the leader of the Gulf Cartel, whose former boss Mario Cardenas, alias Fatso, was caught in September.

The Gulf Cartel's power has waned in recent years in a feud with Mexico's most brutal gang, the Zetas, who initially provided protection to the cartel's operations in north-eastern Mexico.

The US government had offered a $5 million bounty for Ramirez, who Washington says controls most of the cocaine and marijuana trafficking to the United States from Matamoros in Tamaulipas state.

Mexico's marines last month arrested the leader of the Zetas, Miguel Angel Trevino, a few kilometres from his hometown of Nuevo Laredo on the US border.

More than 70,000 people were killed during former president Felipe Calderon's six-year offensive against drug cartels and over 6,000 have died since president Enrique Pena Nieto took office in December.